U.S. patent application number 10/187816 was filed with the patent office on 2003-05-08 for absorbent article.
This patent application is currently assigned to UNI-CHARM CORPORATION. Invention is credited to Nishitani, Kazuya, Yoshimasa, Wataru.
Application Number | 20030088231 10/187816 |
Document ID | / |
Family ID | 19047972 |
Filed Date | 2003-05-08 |
United States Patent
Application |
20030088231 |
Kind Code |
A1 |
Yoshimasa, Wataru ; et
al. |
May 8, 2003 |
Absorbent article
Abstract
Disclosed is an absorbent article including a backsheet, an
absorbent storage layer, a liquid guide layer, and a top layer. The
absorbent storage layer, the liquid guide layer and the top layer
satisfy the following relationships: the liquid guide layer>the
absorbent storage layer>the top layer with respect to a water
absorbency due to capillary phenomenon; the liquid guide
layer>the absorbent storage layer>the top layer with respect
to a retention ratio of a liquid dropped onto the top layer in an
amount less than a maximum water absorption amount of the liquid
guide layer; and the absorbent storage layer>the liquid guide
layer>the top layer with respect to a retention ratio of a
liquid dropped onto the top layer in an amount more than the
maximum water absorption amount of the liquid guide layer.
Inventors: |
Yoshimasa, Wataru; (Kagawa,
JP) ; Nishitani, Kazuya; (Kagawa, JP) |
Correspondence
Address: |
DARBY & DARBY P.C.
805 Third Avenue
New York
NY
10022
US
|
Assignee: |
UNI-CHARM CORPORATION
|
Family ID: |
19047972 |
Appl. No.: |
10/187816 |
Filed: |
July 2, 2002 |
Current U.S.
Class: |
604/387 ;
604/385.04 |
Current CPC
Class: |
A61F 13/5376 20130101;
A61F 2013/53721 20130101; A61F 2013/15422 20130101; A61F 13/15203
20130101; A61F 13/53747 20130101; A61F 2013/15463 20130101; A61F
2013/530941 20130101; A61F 13/53713 20130101; A61F 13/4756
20130101 |
Class at
Publication: |
604/387 ;
604/385.04 |
International
Class: |
A61F 013/15 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 12, 2001 |
JP |
2001-212898 |
Claims
What is claimed is:
1. An absorbent article comprising: a backsheet; an absorbent
storage layer; a liquid guide layer; and a top layer formed of at
least one liquid-permeable layer, wherein the backsheet, the
absorbent storage layer, the liquid guide layer, and the top layer
are laminated one upon each other in the order named, wherein the
absorbent storage layer, the liquid guide layer and the top layer
satisfy the following relationships: the liquid guide layer>the
absorbent storage layer>the top layer with respect to a water
absorbency due to capillary phenomenon; the liquid guide
layer>the absorbent storage layer>the top layer with respect
to a retention ratio of a liquid dropped onto the top layer in an
amount less than a maximum water absorption amount of the liquid
guide layer; and the absorbent storage layer>the liquid guide
layer>the top layer with respect to a retention ratio of a
liquid dropped onto the top layer in an amount more than the
maximum water absorption amount of the liquid guide layer.
2. The absorbent article as set forth in claim 1, wherein the
liquid guide layer>the absorbent storage layer with respect to a
diffusion area of a liquid dropped onto the top layer in an amount
more than the maximum water absorption amount of the liquid guide
layer.
3. The absorbent article as set forth in claim 1, wherein the top
layer has a density of 0.01 to 0.1 g/cm.sup.3, the liquid guide
layer has a density of 0.05 to 0.2 g/cm.sup.3, and the density of
the liquid guide layer is larger than the density of the top
layer.
4. The absorbent article as set forth in claim 3, wherein the
absorbent storage layer has a density of 0.05 to 0.2 g/cm.sup.3,
the liquid guide layer has a basis weight of 15 to 150 g/m.sup.2,
the absorbent storage layer has a basis weight of 150 to 850
g/m.sup.2, and the basis weight of the absorbent storage layer is
larger than the basis weight of the liquid guide layer.
5. The absorbent article as set forth in claim 1, wherein the
liquid guide layer has a water absorption capacity of at least 18
times and a water retention capacity of at most 9 times.
6. The absorbent article as set forth in claim 1, wherein the top
layer and the liquid guide layer are joined to each other through
joining means extending in a longitudinal direction of the
absorbent article.
7. The absorbent article as set forth in claim 1, wherein the
absorbent storage layer is formed with compressed grooves, which
are at opposite sides of a longitudinally extending centerline of
the absorbent article and extend at least in the longitudinal
direction, and the water absorbency due to capillary phenomenon of
the compressed grooves is higher than that of the liquid guide
layer.
8. The absorbent article as set forth in claim 1, wherein the
liquid guide layer has a length smaller than that of the absorbent
storage layer and a width smaller than that of the absorbent
storage layer, and longitudinally opposed front and rear edges and
laterally opposed side edges of the liquid guide layer are inwardly
spaced apart from longitudinally opposed front and rear edges and
laterally opposed side edges of absorbent storage layer.
9. The absorbent article as set forth in claim 7, wherein an area
of the liquid guide layer is smaller than those of the top layer
and the absorbent storage layer, and the liquid guide layer is
positioned between the compressed grooves.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an absorbent article
including sanitary napkin, disposable diaper, urine absorbing pad
and the like. More particularly, the present invention relates to
an absorbent article which has a superior liquid absorption
capacity and gives less discomfort that will be caused by contact
between the bodily waste absorbed therein and the wearer's
skin.
[0003] 2. Description of the Related Art
[0004] Absorbent articles such as sanitary napkin are generally
constructed to include a liquid-impermeable backsheet, an absorbent
layer laid on it, and a liquid-permeable topsheet covering the
absorbent layer. A menstrual blood as bodily waste passes through
the topsheet and is retained by the absorbent layer.
[0005] When the absorbent article of this kind is attached to the
wearer's body, it is required to prevent a liquid, which cannot be
absorbed by the absorbent layer, from leaking outwardly beyond side
edges of the absorbent article. In order to improve the wearing
feel, it is also required to prevent the bodily waste once absorbed
by the absorbent layer from oozing to the surface of the topsheet
and coming into contact with the wearer's skin as much as
possible
[0006] In order to prevent the lateral leakage of the bodily waste
beyond the side edges of the absorbent article, there has been
developed an absorbent article having a nonwoven web disposed
between the body fluid absorbent pad (absorbent layer) and the
topsheet. In Japanese Unexamined Patent Publication No. H7-500759
(500759/1995), for example, there is disclosed an absorbent
material having a nonwoven web between the liquid absorbent pad and
the liquid-permeable topsheet.
[0007] In the absorbent material disclosed in the above-mentioned
Patent Publication, the nonwoven web is provided with a screen
pattern having high fiber density portions being oriented mainly in
the longitudinal direction of the liquid absorbent pad. Therefore,
a bodily waste having passed through the topsheet is diffused
mainly in the longitudinal direction along the high density
portions of the nonwoven web, thereby preventing the lateral
leakage of the liquid.
[0008] As set forth above, the Patent Publication discloses an
invention in which the nonwoven web is disposed between the
topsheet and the liquid absorbent pad in order to diffuse the
bodily waste mainly in the longitudinal direction of the liquid
absorbent pad for absorption by the liquid absorbent pad. However,
in this absorbent material having the nonwoven web mainly for
liquid diffusion, there still remains a problem that when a
pressure is applied from the wearer's skin, a liquid, which is not
absorbed by the liquid absorbent pad but remains diffused in the
nonwoven web, oozes to the surface of the topsheet and adheres to
the wearer's skin again, giving discomfort due to wet feel to the
wearer.
SUMMARY OF THE INVENTION
[0009] The present invention has been worked out in view of the
shortcoming in the prior art set forth above. It is therefore an
object of the present invention to provide an absorbent article
having a good wearing feel, in which a liquid given to a top layer
can rapidly migrate to an absorbent storage layer to prevent a
liquid return to a surface of a top layer.
[0010] According to the invention, there is provided an absorbent
article comprising:
[0011] a backsheet;
[0012] an absorbent storage layer;
[0013] a liquid guide layer; and
[0014] a top layer formed of at least one liquid-permeable layer,
wherein the backsheet, the absorbent storage layer, the liquid
guide layer, and the top layer are laminated one upon each other in
the order named, wherein
[0015] the absorbent storage layer, the liquid guide layer and the
top layer satisfy the following relationships:
[0016] the liquid guide layer>the absorbent storage layer>the
top layer with respect to a water absorbency due to capillary
phenomenon;
[0017] the liquid guide layer>the absorbent storage layer>the
top layer with respect to a retention ratio of a liquid dropped
onto the top layer in an amount less than a maximum water
absorption amount of the liquid guide layer; and
[0018] the absorbent storage layer>the liquid guide layer>the
top layer with respect to a retention ratio of a liquid dropped
onto the top layer in an amount more than the maximum water
absorption amount of the liquid guide layer.
[0019] In the absorbent article according to the present invention,
since the water absorbency due to capillary phenomenon of the
liquid guide layer is higher than that of the top layer, a liquid
given to the top layer is rapidly absorbed by the liquid guide
layer underlying it while being diffused therein. Therefore, the
liquid is hardly stored in the top layer, reducing a wet feel on
the surface of the top layer. On the other hand, since the water
absorbency of the absorbent storage layer is lower than that of the
liquid guide layer, a liquid, which is diffused and absorbed in the
liquid guide layer and then introduced into the absorbent storage
layer, is mainly guided along the thickness direction of the
absorbent storage layer while being prevented from diffusing along
the plane of the absorbent storage layer. Therefore, the liquid
absorbed and retained by the absorbent storage layer does not
excessively diffuse either longitudinally or laterally of the
absorbent article, thereby preventing the possibility of lateral
leakage.
[0020] In case where a small amount of liquid is given to the top
layer, the liquid is immediately absorbed from the top layer to the
liquid guide layer. In case where a relatively large amount of
liquid is given to the top layer, on the other hand, the liquid is
first absorbed by the liquid guide layer, and after the liquid
guide layer is saturated with the liquid, the liquid is then
absorbed by the absorbent storage layer having a higher water
absorbency than the top layer. Thus, the absorbent article has a
large liquid absorption capacity as a whole, and liquid return to
the top layer is prevented.
[0021] As set forth above, since the liquid diffused and absorbed
in the liquid guide layer is then absorbed by the absorbent storage
layer while being prevented from diffusing along the plane of the
absorbent storage layer, the liquid guide layer>the absorbent
storage layer with respect to a diffusion area of a liquid dropped
onto the top layer in an amount more than the maximum water
absorption amount of the liquid guide layer.
[0022] For example, it is preferred that the top layer has a
density of 0.01 to 0.1 g/cm.sup.3, the liquid guide layer has a
density of 0.05 to 0.2 g/cm.sup.3, and the density of the liquid
guide layer is larger than the density of the top layer. In this
case, the water absorbency of the liquid guide layer can be made
higher than that of the top layer, as set forth above, so that the
liquid given to the top layer can be rapidly absorbed by the liquid
guide layer while diffusing therein.
[0023] It is also preferred that the absorbent storage layer has a
density of 0.05 to 0.2 g/cm.sup.3, the liquid guide layer has a
basis weight of 15 to 150 g/m.sup.2, the absorbent storage layer
has a basis weight of 150 to 850 g/m.sup.2, and the basis weight of
the absorbent storage layer is larger than the basis weight of the
liquid guide layer. In this case, it is also preferred that the
density of the liquid guide layer is larger than the density of the
absorbent storage layer. With the basis weight of the absorbent
storage layer being larger than the basis weight of the liquid
guide layer, the liquid saturating the liquid guide layer can be
easily absorbed by the absorbent storage layer in the thickness
direction thereof, thereby increasing the liquid absorption
capacity of the absorbent storage layer and also increasing the
liquid retention capacity of the entire absorbent article.
[0024] Preferably, the liquid guide layer has a water absorption
capacity of at least 18 times and a water retention capacity of at
most 9 times. If the water absorption capacity is at least 18
times, the liquid once absorbed by the liquid guide layer hardly
returns to the top layer. If the water retention capacity is at
most 9 times, on the other hand, the liquid can be easily
discharged from the liquid guide layer to the absorbent storage
layer.
[0025] Preferably, the top layer and the liquid guide layer are
joined to each other through joining means extending in a
longitudinal direction of the absorbent article. In this case, the
liquid given to the top layer can be absorbed by the liquid guide
layer while being oriented in the longitudinal direction of the
absorbent article, thereby suppressing the liquid diffusion
laterally of the absorbent article.
[0026] Preferably, the absorbent storage layer is formed with
compressed grooves, which are at opposite sides of a longitudinally
extending centerline of the absorbent article and extend at least
in the longitudinal direction, and the water absorbency due to
capillary phenomenon of the compressed grooves is higher than that
of the liquid guide layer. With such compressed grooves, a liquid
tending to flow laterally is easily guided in the longitudinal
direction along the compressed grooves, thereby preventing lateral
diffusion of the liquid.
[0027] Preferably, the liquid guide layer has a length smaller than
that of the absorbent storage layer and a width smaller than that
of the absorbent storage layer, and longitudinally opposed front
and rear edges and laterally opposed side edges of the liquid guide
layer are inwardly spaced apart from longitudinally opposed front
and rear edges and laterally opposed side edges of absorbent
storage layer. In this case, the liquid discharged from the liquid
guide layer to the absorbent storage layer upon saturation of the
liquid guide layer can be centered at the central region of the
absorbent storage layer, thereby preventing disadvantageous liquid
diffusion in the absorbent storage layer toward the front and rear
edges and the side edges thereof.
[0028] Preferably, an area of the liquid guide layer is smaller
than those of the top layer and the absorbent storage layer, and
the liquid guide layer is positioned between the compressed
grooves. With the liquid guide layer positioned between the
compressed grooves, the liquid absorbed from the liquid guide layer
to the absorbent storage layer can be prevented from diffusing
toward the front and rear edges and the side edges of the absorbent
storage layer beyond the compressed grooves.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The present invention will be understood more fully from the
detailed description given hereinafter and from the accompanying
drawings of the preferred embodiment of the present invention,
which, however, should not be taken to be limitative to the
invention, but are for explanation and understanding only.
[0030] In the drawings:
[0031] FIG. 1 is a top plan view showing a sanitary napkin as an
absorbent article according to one embodiment of the present
invention, as viewed from a wearer-facing side;
[0032] FIG. 2 is a cross sectional view taken along line II-II of
FIG. 1;
[0033] FIG. 3 is a longitudinal sectional view taken along line
III-III of FIG. 1; and
[0034] FIG. 4 is an enlarged view of a portion of FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0035] The present invention will be discussed hereinafter in
detail in terms of the preferred embodiment according to the
present invention with reference to the accompanying drawings. In
the following description, numerous specific details are set forth
in order to provide a thorough understanding of the present
invention. It will be obvious, however, to those skilled in the art
that the present invention may be practiced without these specific
details. In other instance, well-known structures are not shown in
detail in order to avoid unnecessary obscurity of the present
invention.
[0036] FIG. 1 is a top plan view showing a sanitary napkin 1 as an
absorbent article according to one embodiment of the present
invention. FIG. 2 is a cross sectional view of the sanitary napkin
1 taken along line II-II of FIG. 1, and FIG. 3 is a longitudinal
sectional view of the sanitary napkin 1 taken along line III-III
(longitudinally extending centerline O-O) of FIG. 1.
[0037] The sanitary napkin 1 shown in FIGS. 1 to 3 is to be worn by
a female during menstruation while being attached to an inner side
of a crotch portion of an undergarment.
[0038] As seen from the top plan view of FIG. 1, the sanitary
napkin 1 has a generally arcuate front edge 1a and a rear edge 1b
which is also arcuate but extended longer in the width direction
(X-direction) than the front edge 1a. Right-hand and left-hand side
edges 1c and 1d are curved. The distance between the right-hand
side edge 1c and the left-hand side edge 1d, i.e., the width
(dimension in the X-direction) of the sanitary napkin 1 is larger
in a rear portion on the side of the rear edge 1b, which is to be
brought into contact mainly with the wearer's buttocks, than in a
front portion on the side of the front edge 1a, which is to be
brought into contact mainly with the wearer's crotch. The
right-hand side edge 1c and the left-hand side edge 1d are
protruded laterally (in the X-direction) outwardly in a position
offset toward the front edge 1a from a laterally extending
centerline of the sanitary napkin 1, thereby forming wing portions
2 and 2'.
[0039] As shown in FIGS. 2 and 3, the sanitary napkin 1 comprises a
liquid-impermeable backsheet 3 and first and second
liquid-permeable topsheets 4 and 5. In the embodiment shown, a
liquid-permeable top layer 11 is composed of the first and second
topsheets 4 and 5. Between the backsheet 3 and the first and second
topsheets 4 and 5, there is provided an absorbent storage layer
(absorbent core) 6 capable of absorbing a liquid and retaining the
absorbed liquid.
[0040] In addition, between the first and second topsheets 4 and 5
and the absorbent storage layer 6, there is provided a liquid guide
layer (wicking layer) 7 capable of absorbing a liquid given to the
first and second topsheets 4 and 5 and discharging the liquid into
the absorbent storage layer 6.
[0041] The backsheet 3 has a front edge 3a, a rear edge 3b, a
right-hand side edge 3c and a left-hand side edge 3d. The first
topsheet 4 is in the uppermost position and forms a surface to be
brought into contact with the wearer's skin. The first topsheet 4
has a front edge 4a, a rear edge 4b, a right-hand side edge 4c and
a left-hand side edge 4d. The front edge 3a, the rear edge 3b, the
right-hand side edge 3c and the left-hand side edge 3d of the
backsheet 3 substantially coincide with the front edge 4a, the rear
edge 4b, the right-hand side edge 4c and the left-hand side edge 4d
of the first topsheet 4, respectively. The outline of the sanitary
napkin 1 is defined by the respective edges of the backsheet 3 and
the first topsheet 4.
[0042] The second topsheet 5 is positioned beneath the first
topsheet 4 and has a width (dimension in the X-direction) smaller
than that of the first topsheet 4. The length (dimension in the
Y-direction) of the second topsheet 5 substantially coincides with
that of the first topsheet 4, so that the second topsheet 5 extends
over the entire length of the sanitary napkin 1 along the
centerline O-O.
[0043] The first and second topsheets 4 and 5 may be formed of
nonwoven fabrics having the same fiber density. Here, the second
topsheet 5 may be formed of a single nonwoven fabric either
unfolded or folded. Alternatively, the second topsheet 5 may be
formed by stacking a plurality of nonwoven fabrics. It is also
possible to vary the fiber density between the first and second
topsheets 4 and 5. In this case, it is preferred that the second
topsheet 5 has a higher fiber density than the first topsheet 4. If
so, a liquid given to the first topsheet 4 can be introduced into
the second topsheet 5, thereby preventing the occurrence of
residual liquid on the first topsheet 4.
[0044] In the embodiment shown, the top layer is composed of the
first and second topsheets 4 and 5. However, it is, of course,
possible to form the top layer of a single topsheet.
[0045] As shown in FIGS. 2 and 3, the absorbent storage layer 6 is
disposed on the backsheet 3. This absorbent storage layer 6 has a
given thickness and has a periphery of a front edge 6a, a rear edge
6b, a right-hand side edge 6c and a left-hand side edge 6d, as
shown in broken line in FIG. 1. The front and rear edges 6a and 6b
of the absorbent storage layer 6 are similar in shape to the front
and rear edges 1a and 1b of the sanitary napkin 1. The right-hand
and left-hand side edges 6c and 6d of the absorbent storage layer 6
are similar in shape to the right-hand and left-hand side edges 1c
and 1d of the sanitary napkin 1 except for the portions forming the
wing portions 2 and 2'.
[0046] The front edge 6a, the rear edge 6b, the right-hand side
edge 6c and the left-hand side edge 6d of the absorbent storage
layer 6 are inwardly spaced apart form the front edge 1a, the rear
edge 1b, the right-hand side edge 1c and the left-hand side edge 1d
of the sanitary napkin 1 by 3 to 10 mm. In a region outside of the
periphery (i.e., the front edge 6a, the rear edge 6b, the
right-hand side edge 6c and the left-hand side edge 6d) of the
absorbent storage layer 6, the backsheet 3 and the first topsheet 4
are bonded to each other either directly or through the second
topsheet 5 using a hot-melt adhesive or the like.
[0047] As shown in FIGS. 1 and 2, the liquid guide layer 7 is
disposed between the second topsheet 5 and the absorbent storage
layer 6. The liquid guide layer 7 has a length (dimension in the
Y-direction) smaller than that of the absorbent storage layer 6 and
a width (dimension in the X-direction) smaller than that of the
absorbent storage layer 6, so that the area of the liquid guide
layer 7 is smaller than that of the absorbent storage layer 6. More
specifically, as shown in FIG. 1, the front and rear edges 7a and
7b of the liquid guide layer 7 is positioned closer to the center
of the sanitary napkin 1 than the front and rear edges 6a and 6b of
the absorbent storage layer 6, and the right-hand and left-hand,
side edges 7c and 7d of the liquid guide layer 7 is also positioned
closer to the center of the sanitary napkin 1 than the right-hand
and left-hand side edges 6c and 6d of the absorbent storage layer
6. Furthermore, the right-hand and left-hand side edges 7c and 7d
of the liquid guide layer 7 is positioned closer to the centerline
O-O than the right-hand and left-hand side edges 5c and 5d of the
second topsheet 5.
[0048] As shown in FIG. 2, the lower surface (undergarment-facing
surface) of the second topsheet 5 and the upper surface
(wearer-facing surface) of the liquid guide layer 7 are facing each
other and are bonded to each other with adhesives 9 and 9' being
adopted as joining means. On the other hand, the lower surface of
the liquid guide layer 7 and the upper surface of the absorbent
storage layer 6 are facing each other and are bonded to each other
with adhesives 10 and 10' being adopted as joining means.
[0049] The adhesives 9 and 9' are applied such that they are at
opposite sides of the centerline O-O and extend in the longitudinal
direction just inside the right-hand and left-hand side edges 7c
and 7d of the liquid guide layer 7. Similarly, the adhesives 10 and
10' are applied such that they are at opposite sides of the
centerline O-O and extend in the longitudinal direction just inside
the right-hand and left-hand side edges 7c and 7d of the liquid
guide layer 7.
[0050] Accordingly, a menstrual blood attracted by the liquid guide
layer 7 through the top layer 11 composed of the first and second
topsheets 4 and 5 hardly moves laterally beyond the right-hand and
left-hand side edges 7c and 7d, on the surfaces of the liquid guide
layer 7. Especially when the adhesives 9 and 9' and the adhesives
10 and 10' are mixed with a hydrophilic or water-repellent
material, the liquid attracted by the liquid guide layer 7 through
the top layer 11 can be effectively prevented from moving laterally
beyond the adhesive layers, so that it can be absorbed by the
liquid guide layer 7 while being diffused mainly along the
longitudinal direction. Thus, the lateral leakage of the menstrual
blood from the sanitary napkin 1 can be prevented.
[0051] Here, the joining means for joining the second topsheet 5
and the liquid guide layer 7 and the joining means for joining the
liquid guide layer 7 and the absorbent storage layer 6 should not
be limited to the adhesives. For example, heat-sealing may be
performed along the longitudinal direction just inside the
right-hand and left-hand side edges 7c and 7d of the liquid guide
layer 7.
[0052] As shown in FIGS. 1, 2 and 3, the sanitary napkin 1 is
formed with a compressed groove 8 surrounding the liquid guide
layer 7. When the skin-contacting side of the sanitary napkin 1 is
viewed from above, the compressed groove 8 is in an hourglass
shape.
[0053] In the compressed groove 8, the first topsheet 4, the
absorbent storage layer 6 and the backsheet 3 are heated under
pressure, so that the absorbent storage layer 6 is compressed and
recessed, and the first topsheet 4 is laid thereon in conformity
with the recess. The embossing pattern for forming the compressed
groove 8 may be either a pattern of continuous line or a pattern of
intermittent embossments.
[0054] The width of the compressed groove 8 is preferably from 0.5
to 5 mm. If the width is less than 0.5 mm, the sanitary napkin 1 is
liable to be cut at the compressed groove 8 during wear,
deteriorating the durability of the sanitary napkin 1. If the width
is more than 5 mm, the stiffness of the sanitary napkin 1 is
excessively increased, resulting in causing a clearance between the
wearer's body and the sanitary napkin 1 during wear. Therefore, a
menstrual blood may possibly leak out of the sanitary napkin 1.
More preferred range of the width of the compressed groove 8 is
from 1.5 to 3 mm.
[0055] Next, liquid absorbency characteristics of the top layer 11
composed of the first and second topsheets 4 and 5, the absorbent
storage layer 6, the liquid guide layer 7, and the compressed
groove 8 will be described. Here, it should be noted that the fist
and second topsheets 4 and 5 composing the top layer 11 in the
shown embodiment are described as having the same density, basis
weight and thickness.
[0056] (Water Absorbency by Klemm's Method)
[0057] The relationship of the first and second topsheets 4 and 5,
the absorbent storage layer 6, and the liquid guide layer 7 will be
described with respect to the water absorbency due to capillary
phenomenon.
[0058] For measurement of the water absorbency by Klemm's method,
the sheet materials of the first topsheet 4 and the second topsheet
5 are cut into separate samples having a length of 100 mm in MD
(Machine direction) thereof and a width of 25 mm in CD (Cross
direction) thereof. Likewise, the sheet materials of the absorbent
storage layer 6 and the liquid guide layer 7 are cut into samples
having a length of 100 mm in MD thereof and a width of 25 mm in CD
thereof. It should be noted that the first and second topsheets 4
and 5, the absorbent storage layer 6, and the liquid guide layer 7
are used in the sanitary napkin 1 such that MDs of their sheet
materials coincide with the longitudinal direction (Y-direction) of
the sanitary napkin 1.
[0059] The samples thus prepared are suspended with MDs coinciding
with the vertical direction, and then, the lower ends of the
samples having a length of 15 mm are immersed in distilled water
colored with a dye. Other conditions are in conformity to
JIS-P8141. Water absorption heights after one minute are
measured.
[0060] At this time, the relationship with respect to the water
absorbency by Klemm's Method is required that the liquid guide
layer 7>the absorbent storage layer 6>the first and second
topsheets 4 and 5. With the water absorbency of the liquid guide
layer 7 being set higher than that of the first and second
topsheets 4 and 5, a menstrual liquid given to the first and second
topsheets 4 and 5 can be absorbed by the liquid guide layer 7 below
them, thereby preventing the occurrence of residual menstrual blood
in the first and second topsheets 4 and 5. Therefore, the area and
time of contact between the menstrual blood absorbed by the
sanitary napkin 1 and the wearer's skin can be reduced, giving no
discomfort to the wearer.
[0061] On the other hand, since the water absorbency of the
absorbent storage layer 6 is set lower than that of the liquid
guide layer 7, the liquid absorbed by and diffused in the liquid
guide layer 7 is introduced into the absorbent storage layer 6
mainly along the thickness direction thereof while being prevented
from diffusing along the plane of the absorbent storage layer 6.
Therefore, the liquid absorbed and retained by the absorbent
storage layer 6 does not excessively diffuse either in the
longitudinal direction or in the width direction, thereby
preventing the possibility of lateral leakage.
[0062] Here, in order to rapidly absorb a liquid given to the first
and second topsheets 4 and 5 by the liquid guide layer 7, the water
absorbency by Klemm's Method of the liquid guide layer 7 is
preferably at least 40 mm, more preferably at least 50 mm.
[0063] Furthermore, when the water absorbency by Klemm's Method is
measured for a sample, which is prepared by cutting the sheet
material of the absorbent storage layer 6 to have a length of 100
mm in MD thereof and a width of 25 mm in CD thereof and then
compressing the entire sample under the same condition as that for
the compressed groove 8 of the sanitary napkin 1, the relationship
with respect to the water absorbency by Klemm's Method is required
that the compressed sample (the compressed groove 8)>the liquid
guide layer 7>the absorbent storage layer 6>the first and
second topsheets 4 and 5. With such relationship, when a menstrual
blood absorbed in a region inside the compressed groove 8 reaches
the compressed groove 8, such menstrual blood moves in the
longitudinal direction along the compressed groove 8, thereby
preventing the menstrual blood from moving beyond the compressed
groove 8 and leaking outwardly, especially laterally.
[0064] (Liquid Retention Ratio)
[0065] At first, the maximum water absorption amount (water
absorption saturation amount) of the liquid guide layer 7 is
measured. A sample is prepared by cutting the sheet material of the
liquid guide layer 7 employed for the sanitary napkin 1 into the
same size as that of the liquid guide layer 7, and the weight of
the sample is measured. Then, the sample is immersed in an
artificial menstrual blood and taken out one minute later. After
standing for one minute on a wire net, the weight of the sample is
measured again. The maximum water absorption amount is obtained by
subtracting the sample weight before absorption of the artificial
menstrual blood from the sample weight after absorption of the
artificial menstrual blood.
[0066] Here, the artificial menstrual blood contains 10% by weight
of glycerin, 1% by weight of carboxymethyl cellulose and the
balance being distilled water.
[0067] Next, the artificial menstrual blood is applied to the first
topsheet 4 near the center of the liquid guide layer 7 of the
sanitary napkin 1. At this time, the artificial menstrual blood is
applied at a rate of 7 g/minute in an amount (e.g., 3 g) less than
the maximum water absorption amount of the liquid guide layer 7.
The artificial menstrual blood is also applied to the first
topsheet 4 of another sanitary napkin 1 at a rate of 7 g/minute in
an amount (e.g., 15 g) more than the maximum water absorption
amount of the liquid guide layer 7. One minute after application of
the artificial menstrual blood, the respective liquid retention
ratios of the first and second topsheets 4 and 5, the liquid guide
layer 7, and the absorbent storage layer 6 are measured for the
respective sanitary napkins.
[0068] Here, the liquid retention ratio is obtained by
{(.beta.-.alpha.)/.gamma.}.times.100 (%). In case of the liquid
guide layer 7, the weight of the liquid guide layer 7 before
application of the artificial menstrual blood is ".alpha.", the
weight of the liquid guide layer 7 after application of the
artificial menstrual blood is ".beta.", and the weight of the
artificial menstrual blood dropped onto the first topsheet 4 is
".gamma." (in the above case, 3 g or 15 g). The first and second
topsheets 4 and 5 are tested as a unit to obtain the liquid
retention ratio of the top layer 11. In case of the absorbent
storage layer 6, too, the liquid retention ratio is obtained
similar to the case of the liquid guide layer 7.
[0069] In the sanitary napkin 1, the relationship of the layers
with respect to the liquid retention ratio is such that:
[0070] the liquid guide layer 7>the absorbent storage layer
6>the top layer 11 (the first and second topsheets 4 and 5),
when the artificial menstrual blood is applied in an amount (e.g.,
3 g) less than maximum water absorption amount of the liquid guide
layer 7; and
[0071] the absorbent storage layer 6>the liquid guide layer
7>the top layer 11 (the first and second topsheets 4 and 5),
when the artificial menstrual blood is applied in an amount (e.g.,
15 g) more than maximum water absorption amount of the liquid guide
layer 7.
[0072] With the relationship of the layers with respect to the
liquid retention ratio being thus set, when a small amount of
menstrual blood is given to the first topsheet 4 of the sanitary
napkin 1, such a small amount of menstrual blood is rapidly
absorbed by the liquid guide layer 7 from the first and second
topsheets 4 and 5, and retained by the liquid guide layer 7. On the
other hand, when a large amount of menstrual blood is given to the
first topsheet 4 and the amount of the menstrual blood absorbed by
the liquid guide layer 7 exceeds the maximum water absorption
amount thereof, the menstrual blood is discharged from the liquid
guide layer 7 to the absorbent storage layer 6 and stored in the
absorbent storage layer 6.
[0073] Here, since the water absorbency of the absorbent storage
layer 6 is higher than those of the first and second topsheets 4
and 5, the menstrual liquid introduced into the liquid guide layer
7 in an amount more than the maximum water absorption amount of the
liquid guide layer 7 is hardly attracted by the first and second
topsheets 4 and 5 from the liquid guide layer 7, but is absorbed
and retained mainly by the absorbent storage layer 6. At this time,
since the water absorbency of the absorbent storage layer 6 is
lower than that of the liquid guide layer 7, as set forth above,
the liquid migrating from the liquid guide layer 7 to the absorbent
storage layer 6 is hardly diffused along the plane of the absorbent
storage layer 6, but is absorbed by the absorbent storage layer 6
mainly along the thickness direction of the absorbent storage layer
6.
[0074] (Porosity of Top Layer 11)
[0075] The porosities of the first and second topsheets 4 and 5
after compression in a wet state are preferably at least 93%, more
preferably at least 95%. If the porosities are less than 93%, a
menstrual blood hardly passes through the first and second
topsheets 4 and 5, so that the liquid guide layer 7 disposed
beneath the second topsheet 5 cannot rapidly transport the
menstrual blood to the absorbent storage layer 6.
[0076] For measurement of the porosities of the first and second
topsheets 4 and 5 after compression in a wet state, the sheet
materials of the first topsheet 4 and the second topsheet 5 are cut
into samples having a size of 100 mm (in MD).times.100 mm (in CD),
and then, their basis weights are measured (the basis weight is
represented by ".nu."). Then, 3 g of the artificial menstrual blood
is dropped onto the sample put on a filter paper, and the sample is
allowed to stand for one minute. Thereafter, a pressure of 3.43 kPa
is applied to the sample for three minutes. One minute after
removal of the pressure, the thickness of the sample is measured
(the thickness is represented by ".xi."). The porosity after
compression in a wet state is calculated by [1-(.nu./.xi.)]/(fiber
density).times.100. The term "fiber density" as used herein refers
to a density of the sample in a dry state.
[0077] (Water Absorption Capacity and Water Retention Capacity of
Liquid Guide Layer 7)
[0078] It is preferred that the liquid guide layer 7 has a water
absorption capacity (water absorption magnification) of at least 18
times and a water retention capacity (water retention
magnification) of at most 9 times, as measured by applying the
artificial menstrual blood.
[0079] If the water absorption capacity of the liquid guide layer 7
is less than 18 times, the amount of liquid which can be
temporarily retained by the liquid guide layer 7 becomes
excessively small, so that the menstrual blood is liable to return
to the first and second topsheets 4 and 5. If the water retention
capacity of the liquid guide layer 7 is more than 9 times, on the
other hand, the menstrual blood hardly moves to the absorbent
storage layer 6. Therefore, a large amount of liquid is retained by
the liquid guide layer 7 close to the wearer's skin, thereby
providing a wet feel to the wearer.
[0080] For measurement of the water absorption capacity of the
liquid guide layer 7, the sheet material of the liquid guide layer
7 is cut out to form a sample having the same size and thickness as
those of the liquid guide layer 7 employed for the sanitary napkin
1, and then, the weight of the sample is measured (this weight is
represented by "a"). Next, the sample is immersed in the artificial
menstrual blood and taken out one minute later. After standing for
one minute on a wire net, the weight of the sample is measured
again (this weight is represented by "b"). The value calculated by
(b/a).times.100 represents the water absorption capacity.
[0081] For measurement of the water retention capacity of the
liquid guide layer 7, the sample after standing for one minute on
the wire net is subjected to an acceleration of 74.5 G for 90
seconds with a centrifugal machine. Thereafter, the weight of the
sample is measured (this weight is represented by "c"). The value
calculated by (c/a).times.100 represents the water retention
capacity.
[0082] (Liquid Diffusion Property)
[0083] The liquid diffusion property, the absorption speed and the
liquid return ratio (wet back ratio) of the sanitary napkin 1, when
the artificial menstrual blood is applied to the surface of the
first topsheet 4 in an amount more than the maximum water
absorption amount of the liquid guide layer 7, are determined as
follows.
[0084] For measurement, 3 g of the artificial menstrual blood is
applied to the first topsheet 4 of the sanitary napkin 1 in the
period of 2 seconds, and 30 seconds later, 4 g of the artificial
menstrual blood is applied thereto in the period of 2 seconds. One
minute later, a filter paper is laid thereon and a pressure of 3.43
kPa is applied for 3 minutes. Immediately after removal of the
pressure, 3 g of the artificial menstrual blood is applied thereto
in the period of 2 seconds, and the time required for the
artificial menstrual blood to penetrate into the sanitary napkin 1
from the surface of the first topsheet 4 and disappear from the
surface of the first topsheet 4 is taken as the liquid absorption
speed of the sanitary napkin 1.
[0085] Thereafter, 30 seconds later, 4 g of the artificial
menstrual blood is dropped in the period of 2 seconds, and one
minute later, a filter paper is laid thereon and a load of 3.43 kPa
is applied for 3 minutes. In case where the weight of a liquid
absorbed by the filter paper is "m" g, the liquid return ratio (wet
back ratio) when a liquid is applied in an amount more than the
maximum water absorption amount of the liquid guide layer 7 is
represented by (m/14).times.100 (%). It should be noted that "14"
in the formula refers to the total weight (G) of the applied
liquid. Furthermore, after removal of the filter paper, the
diffusion dimension of the menstrual blood is measured for the
liquid guide layer 7 and the absorbent storage layer 6,
respectively.
[0086] In the sanitary napkin 1, the liquid diffusion dimension
(area) is preferably larger in the liquid guide layer 7 than in the
absorbent storage layer 6.
[0087] On the other hand, the liquid absorption speed is preferably
equal to or less than 30 seconds, more preferably equal to or less
than 25 seconds. The liquid return ratio is preferably equal to or
less than 68%, more preferably equal to or less than 60%. In case
where the liquid absorption speed is equal to or less than 30
seconds and the liquid return ratio is equal to or less than 68%, a
wet feel to the wearer's skin can be reduced when the sanitary
napkin 1 is worn.
[0088] Next, materials of the respective layers constructing the
sanitary napkin 1 will be described.
[0089] For example, the first and second topsheets 4 and 5 are
formed of a through-air bonded nonwoven fabric, in which
thermoplastic fibers forming a web are fusion-bonded with heated
air. The fiber density of the through-air bonded nonwoven fabric is
preferably 0.01 to 0.1 g/cm.sup.3. If the fiber density is less
than 0.01 g/cm.sup.3, the number of fiber crossover points is
small, deteriorating durability as the topsheet. If the fiber
density is more than 0.1g/cm.sup.3, the liquid permeability is
deteriorated, so that a menstrual blood hardly penetrates through
it to the liquid guide layer 7. More preferred range of the density
is 0.01 to 0.06 g/cm.sup.3.
[0090] Fibers forming the through-air bonded nonwoven fabric are
made of polyolefin macromolecule or polyester macromolecule. The
fibers are preferably bicomponent synthetic fibers of sheath/core
structure such as PET/PE or PP/PE, more preferably bicomponent
synthetic fibers of eccentric (off-center) structure or hollow
structure. In an alternative, the fibers may be, without
limitation, bicomponent synthetic fibers of side-by-side structure
such as PP/PP. These synthetic fibers are preferably treated to be
hydrophilic by coating or mixing a hydrophilic agent. In an
alternative, the through-air bonded nonwoven fabric may be made
hydrophilic by mixing the hydrophobic synthetic fibers with
hydrophilic fibers such as viscose rayon, acetate rayon or cotton
fibers.
[0091] The diameter of the fibers forming the through-air bonded
nonwoven fabric is preferably 10 to 50 .mu.m, more preferably 15 to
35 .mu.m. If the fiber diameter is less than 10 .mu.m, when the
fibers are accumulated into a fiber web, the distance between
adjacent fibers becomes small, so that necessary porosity cannot be
obtained. If the fiber diameter is more than 50 .mu.m, on the other
hand, the fiber stiffness is increased to give a foreign body
sensation to the wearer.
[0092] The basis weight of the top layer 11 (total basis weight of
the through-air bonded nonwoven fabrics forming the first and
second topsheets 4 and 5) is preferably 15 to 120 g/m.sup.2. If the
basis weight is less than 15 g/m.sup.2, since the distance between
the wearer-facing surface of the top layer 11 and the liquid guide
layer 7 is small, the menstrual blood retained by the liquid guide
layer 7 is liable to return to the wearer-facing surface of the top
layer 11 through the first and second topsheets 4 and 5, thereby
causing the possibility of giving a wet feel due to the menstrual
blood to the wearer. If the basis weight is more than 120
g/m.sup.2, on the other hand, it takes a long time for the
menstrual blood discharged onto the wearer-facing surface of the
top layer 11 to reach the liquid guide layer 7, so that the liquid
guide layer 7 cannot rapidly absorb the menstrual blood. More
preferred range of the basis weight of the top layer 11 is 50 to 90
g/m.sup.2.
[0093] It should be noted that the first and second topsheets 4 and
5 are not limited to such through-air bonded nonwoven fabric. For
example, an open-cell foamed resin material may be employed.
[0094] As shown in a partial sectional view of FIG. 4, the top
layer 11 composed of the first and second topsheets 4 and 5 may be
formed with a large number of liquid passages 12 continuously
passing through the first and second topsheets 4 and 5. These
liquid passages 12 can be formed by piercing the laminate of the
first and second topsheets 4 and 5 with needles. In this case,
since the liquid guide layer 7 is exposed through the liquid
passages 12, the menstrual blood given to the top layer 11 can be
immediately absorbed by the liquid guide layer 7 through the liquid
passages 12, thereby increasing the speed of absorbing the liquid
by the liquid guide layer 7 through the top layer 11.
[0095] For example, the liquid guide layer 7 is formed of a
spunlaced nonwoven fabric. The spunlaced nonwoven fabric means a
nonwoven fabric in which accumulated fibers forming a web are
entangled with jets of water to have high fiber density regions and
low fiber density regions alternated both in MD and CD. In
addition, by applying the water jets to the accumulated fiber web
on a wire having a large number of apertures for entanglement, the
nonwoven fabric can be formed with openings. In the case where the
liquid guide layer 7 is formed of the spunlaced nonwoven fabric
having the high and low density regions and the openings, the
liquid is effectively permeated through the high density region and
retained by the opening, providing superior water absorptive power
and superior liquid diffusion property.
[0096] The fiber density of the spunlaced nonwoven fabric forming
the liquid guide layer 7 is preferably 0.05 to 0.2 g/cm.sup.3. If
the fiber density is less than 0.05 g/cm.sup.3, the force to
attract the menstrual blood discharged on the first and second
topsheets 4 and 5 to the liquid guide layer 7 is weakened. If the
fiber density is more than 0.2 g/cm.sup.3, on the other hand, the
menstrual blood saturating the liquid guide layer 7 hardly moves to
the absorbent storage layer 6.
[0097] Here, it is required that the fiber density of the liquid
guide layer 7 is higher than the fiber density of the through-air
bonded nonwoven fabric forming the top layer 11. By setting the
difference in fiber density between the top layer 11 and the liquid
guide layer 7, the liquid given to the top layer 11 can be rapidly
absorbed by the liquid guide layer 7.
[0098] The basis weight of the liquid guide layer 7 is preferably
15 to 150 g/m.sup.2. If the basis weight is less than 15 g m.sup.2,
the maximum water absorption amount of the liquid guide layer 7 is
too small. If the basis weight is more than 150 g/m.sup.2, the
water retention amount of the liquid guide layer 7 is excessively
increased, so that the menstrual blood in the liquid guide layer 7
hardly moves to the absorbent storage layer 6.
[0099] The spunlaced nonwoven fabric mainly comprises hydrophilic
regenerated cellulose fibers, preferably rayon fibers such as
viscose rayon or acetate rayon. Alternatively, hydrophilic fibers
such as cotton fibers, synthetic fibers made of polyolefin resin
and treated with a hydrophilic agent to be hydrophilic, or
synthetic fibers made of polyester resin and treated with a
hydrophilic agent to be hydrophilic may be employed for the
spunlaced nonwoven fabric. In order to increase the absorption
speed of the liquid guide layer 7, moreover, the fibers forming the
spunlaced nonwoven fabric are preferably modified cross-section
fibers having a relatively large area/weight ratio, as exemplified
by fibers having a cross-section of C or Y shape.
[0100] It should be noted that the liquid guide layer 7 is not
limited to the spunlaced nonwoven fabric. For example, a laminate
of tissue paper, air-laid pulp, fluff pulp, CTMP or the like may be
employed for the liquid guide layer 7.
[0101] The absorbent storage layer 6 is composed of hydrophilic
fibers, as exemplified by an aggregate of hydrophilic fibers such
as fluff pulp, CTMP, or rayon fibers in which superabsorbent
polymer is dispersed, or a sheet formed by wrapping hydrophilic
fibers, superabsorbent polymer, and the like in air-laid pulp or
tissue paper.
[0102] The fiber density of the absorbent storage layer 6 is
preferably 0.05 to 0.2 g/cm.sup.3. If the fiber density is less
than 0.05 g/cm.sup.3, it is difficult to absorb the menstrual blood
from the liquid guide layer 7. If the fiber density is more than
0.2 g/cm.sup.3, the menstrual blood absorbed by the absorbent
storage layer 6 from the liquid guide layer 7 hardly moves toward
the undergarment-facing surface of the absorbent storage layer 6,
so that the absorbed menstrual blood excessively spreads in the
wearer-facing surface of the absorbent storage layer 6. As set
forth above, the sanitary napkin 1 requires that the water
absorbency of the liquid guide layer 7 be higher than the water
absorbency of the absorbent storage layer 6. To this end, it is
preferred that the density of the liquid guide layer 7 is higher
than that of the absorbent storage layer 6, or that the
hydrophilicity of the fibers forming the liquid guide layer 7 is
higher than that of the fibers forming the absorbent storage layer
6.
[0103] The basis weight of the absorbent storage layer 6 is
preferably 150 to 850 g/m.sup.2. If the basis weight is less than
150 g/m.sup.2, the absorbent storage layer 6 is decreased in
capability of absorbing and retaining water. If the basis weight is
more than 850 g/m.sup.2, on the other hand, the absorbent storage
layer 6 is increased in thickness and stiffness, providing a
foreign body sensation to the wearer. More preferably, the basis
weight is 300 to 750 g/m.sup.2.
[0104] The relationship between the basis weight of the liquid
guide layer 7 and the basis weight of the absorbent storage layer 6
is preferably such that the basis weight of the absorbent storage
layer 6 is at least twice as large as the basis weight of the
liquid guide layer 7. By making the basis weight of the absorbent
storage layer 6 larger than the basis weight of the liquid guide
layer 7, when the menstrual blood is given to the absorbent storage
layer 6 from the liquid guide layer 7, the menstrual blood
retention capacity of the absorbent storage layer 6 can be
increased.
[0105] When the sanitary napkin 1 thus constructed is used, the
menstrual blood given to the top-layer 11 can be rapidly absorbed
by the liquid guide layer 7, thereby making the residual liquid on
the top layer 11 very little. In addition, such menstrual blood is
diffused and retained by the liquid guide layer 7, and when the
menstrual blood saturates the liquid guide layer 7, it is
immediately absorbed by the absorbent storage layer 6. At this
time, the menstrual blood hardly diffuses along the plane of the
absorbent storage layer6, but easily permeates in the thickness
direction of the absorbent storage layer 6. Thus, the absorbent
storage layer 6 can prevent liquid diffusion along its plane,
thereby reducing the possibility of lateral leakage.
[0106] Especially in the foregoing embodiment, since the area of
the liquid guide layer 7 is smaller than that of the absorbent
storage layer 6, the menstrual blood diffused in the liquid guide
layer 7 is absorbed by the absorbent storage layer 6 while being
prevented from diffusing more. Therefore, the menstrual blood
hardly permeates toward the front edge 6a, the rear edge 6b, the
right-hand side edges 6c and the left-hand side edges 6d of the
absorbent storage layer 6, thereby reducing the possibility of
lateral leakage. Furthermore, since the periphery of the liquid
guide layer 7 is surrounded by the compressed groove 8, the
menstrual blood given to the absorbent storage layer 6 from the
liquid guide layer 7 hardly permeates the outer region of the
absorbent storage layer 6 beyond the compressed groove 8.
[0107] Hereinabove, the absorbent article of the present invention
has been described embodied in a sanitary napkin. However, the
absorbent article of the present invention is also applicable to
other absorbent articles such as disposable diaper, urine absorbing
pad, and the like.
EXAMPLES
[0108] As the respective layers of a sanitary napkin having the
same structure as that of FIG. 1, various sheet materials were
prepared. Tables 1 to 4 show the construction and properties of the
respective layers. Table 1 shows the construction and properties of
three kinds of topsheets; Table 2 shows the construction and
properties of five kinds of liquid guide layers; Table 3 shows the
construction and properties of two kinds of absorbent storage
layers; and Table 4 shows the property of the compressed
groove.
1 TABLE 1 Fiber density Porosity Water absorbency by Basic Initial
fiber after compression after compression Klemm's Method weight
density in wet in wet After one Main component (g/m.sup.2)
(g/cm.sup.3) (g/cm.sup.3) (%) minute (mm) Topsheet-1 PE/PP
sheath/core through- 85 0.056 0.05 93.7 1 air bonded nonwoven
Topsheet-2 PE/PP sheath/core through- 85 0.02 0.03 96.8 1 air
bonded nonwoven Topsheet-3 PP spunbonded nonwoven 20 0.066 0.07
92.6 1
[0109]
2 TABLE 2 Water Water Water absorbency Basis weight absorption
retention by Klemm's Method Main component (g/m.sup.2) capacity
capacity After one minute (mm) Liquid guide layer-1 100% rayon
spunlaced nonwoven 75 23.2 7.5 66 Liquid guide layer-2 Rayon/PET
50/50 spunlaced nonwoven 75 19 8.3 58 Liquid guide layer-3 Tissue
paper 75 13.2 4.7 35 Liquid guide layer-4 Air-laid pulp 75 11.8 6.6
54 Liquid guide layer-5 Fluff pulp 75 20 9.1 22
[0110]
3 TABLE 3 Initial Water absorbency Basis weight Thickness fiber
density by Klemm's Method Main component (g/m.sup.2) (mm)
(g/cm.sup.3) After one minute (mm) Absorbent storage layer-1
Pulp/SAP 600/15 8 0.077 22 Absorbent storage layer-2 Pulp/SAP
600/15 3 0.205 24
[0111]
4 TABLE 4 Water absorbency by Klemm's Method After one minute (mm)
Compressed groove 90
Examples
[0112] Preferred combinations of the topsheet, the liquid guide
layer and the absorbent storage layer were selected from Tables 1
to 4 to prepare sanitary napkins of Examples 1, 2, 3, 4 and 5, as
shown in Table 5.
5 TABLE 5 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Topsheet Topsheet-2
Topsheet-2 Topsheet-1 Topsheet-2 Topsheet-2 Liquid guide Liquid
guide Liquid guide Liquid guide Liquid guide Liquid guide layer
layer-1 layer-2 layer-1 layer-3 layer-4 Absorbent storage Absorbent
storage Absorbent storage Absorbent storage Absorbent storage
Absorbent storage Constructions of Examples layer layer-1 layer-1
layer-1 layer-1 layer-1 Evaluation Liquid retention Topsheet 5.4
5.5 5.5 7.5 6.8 result ratio (%) Liquid guide layer 8.7 8.3 8.8 11
15 (at 15 g) Absorbent storage 85.9 86.2 85.7 81.5 78.2 layer
Evaluation of Diffusion dimension 60 61 62 68 65 absorbency (mm) in
length Diffusion dimension 28 27 31 33 32 (mm) in width Liquid
return ratio 55 54 56 68 64 (%) Absorption speed 9.4 9.8 12.2 25 24
(second)
Comparative Examples
[0113] Other combinations of the topsheet, the liquid guide layer
and the absorbent storage layer were selected to prepare sanitary
napkins of Comparative Examples 1, 2, 3, and 4, as shown in Table
6.
6 TABLE 6 Com. Ex. 1 Com. Ex. 2 Com. Ex. 3 Com. Ex. 4 Topsheet
Topsheet-1 Topsheet-2 Topsheet-3 Topsheet-2 Liquid guide layer --
Liquid guide layer-1 Liquid guide layer-1 Liquid guide layer-5
Constructions of Absorbent storage Absorbent storage Absorbent
storage Absorbent storage Absorbent storage Comparative Examples
layer layer-1 layer-2 layer-1 layer-1 Evaluation Liquid retention
Topsheet 7.7 8 12 6.9 result ratio (%) Liquid guide layer 9 10 14.8
(at 15 g) Absorbent storage 92.3 83 78 78.3 layer Evaluation of
Diffusion dimension 70 68 88 67 absorbency (mm) in length Diffusion
dimension 40 46 56 51 (mm) in width Liquid return ratio 69 57 75 74
(%) Absorption speed 41.8 35 42 48 (second)
[0114] <Evaluation>
[0115] In Comparative Example 1, since there was no liquid guide
layer, the absorption speed of the artificial menstrual blood given
to the top layer was low.
[0116] In Comparative Example 2, since the fiber density of the
absorbent storage layer was high, the menstrual blood given from
the liquid guide layer to the absorbent storage layer was
excessively diffused on the wearer-facing surface of the absorbent
storage layer, so that it hardly moved toward the
undergarment-facing surface in the absorbent storage layer.
Therefore, the menstrual blood absorbed by the liquid guide layer
to saturate the liquid guide layer could not be absorbed by the
absorbent storage layer rapidly in the thickness direction thereof,
thereby keeping the saturated state of the liquid guide layer. As a
result, the absorption speed of the menstrual blood given to the
top layer was low.
[0117] In Comparative Example 3, since the porosity of the top
layer was excessively low, the artificial menstrual blood was
easily left in the top layer and the absorption speed of the liquid
from the top layer to the liquid guide layer was low. Therefore,
the migration of the liquid from the liquid guide layer to the
absorbent storage layer was also slow, so that the liquid was
diffused on the wearer-facing surface of the absorbent storage
layer.
[0118] In Comparative Example 4, since the water retention capacity
(water retention magnification) of the liquid guide layer was high,
the artificial menstrual blood hardly migrated from the liquid
guide layer to the absorbent storage layer, so that the absorption
speed was low as a whole.
[0119] In Examples 1 to 5, on the other hand, the liquid diffusion
area in the absorbent storage layer was small, the liquid
absorption speed was equal to or less than 25 seconds, and the
liquid return ratio was equal to or less than 68%. Therefore, when
the sanitary napkins of Examples 1 to 5 are worn, a wet feel to the
wearer's skin can be reduced.
[0120] As has been described above, in the absorbent article of the
present invention, a body fluid discharged onto the top layer can
be guided through the liquid guide layer to the absorbent storage
layer, thereby eliminating return of the body fluid thus absorbed
and retained. In addition, the body fluid absorbed by the absorbent
article hardly diffuses along a plane of the absorbent article,
thereby reducing a wet area due to the absorbed and retained body
fluid. Accordingly, the absorbed body fluid hardly gives a wet feel
to the wearer.
[0121] Although the present invention has been illustrated and
described with respect to exemplary embodiment thereof, it should
be understood by those skilled in the art that the foregoing and
various other changes, omission and additions may be made therein
and thereto, without departing from the spirit and scope of the
present invention. Therefore, the present invention should not be
understood as limited to the specific embodiment set out above but
to include all possible embodiments which can be embodied within a
scope encompassed and equivalent thereof with respect to the
feature set out in the appended claims.
* * * * *